C8 - Advanced SQL

8/7/2019 C8 - Advanced SQL

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Chapter 8:Chapter 8:Advanced SQLAdvanced SQL

Modern Database ManagementModern Database Management

99thth EditionEdition

Jeffrey A. Hoffer, Mary B. Prescott,Jeffrey A. Hoffer, Mary B. Prescott,

Heikki TopiHeikki Topi


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ObjectivesObjectives

Definition of termsDefinition of terms

Write single and multiple table SQL queriesWrite single and multiple table SQL queries

Define and use three types of joinsDefine and use three types of joins Write noncorrelated and correlated subqueriesWrite noncorrelated and correlated subqueries

Establish referential integrity in SQLEstablish referential integrity in SQL

Understand triggers and stored proceduresUnderstand triggers and stored procedures

Discuss SQL:200n standard and its extension ofDiscuss SQL:200n standard and its extension ofSQLSQL--9292

Understand SQL use for OLTP and OLAPUnderstand SQL use for OLTP and OLAP


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Processing Multiple TablesProcessing Multiple TablesJoinsJoins

JoinJoina relational operation that causes two or more tables with aa relational operation that causes two or more tables with acommon domain to be combined into a single table or viewcommon domain to be combined into a single table or view EquiEqui--joinjoina join in which the joining condition is based ona join in which the joining condition is based on

equality between values in the common columns; common columnsequality between values in the common columns; common columnsappear redundantly in the result tableappear redundantly in the result table

Natural joinNatural joinan equian equi--join in which one of the duplicate columnsjoin in which one of the duplicate columnsis eliminated in the result tableis eliminated in the result table Outer joinOuter joina join in which rows that do not have matchinga join in which rows that do not have matching

values in common columns are nonetheless included in the resultvalues in common columns are nonetheless included in the resulttable (as opposed totable (as opposed to innerinner join, in which rows must have matchingjoin, in which rows must have matchingvalues in order to appear in the result table)values in order to appear in the result table)

Union joinUnion joinincludes all columns from each table in the join, andincludes all columns from each table in the join, andan instance for each row of each tablean instance for each row of each table

The common columns in joined tables are usually the primary key of the

dominant table and the foreign key of the dependent table in 1:M relationships


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Figure 8Figure 8--22

Visualization of different join types with resultsVisualization of different join types with results

returned in shaded areareturned in shaded area

Left outer join: Left watch for the sequence of tables


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The following slides create tables forThe following slides create tables for

this enterprise data modelthis enterprise data model


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These tables are used in queries that follow

Figure 8-1 PVFCCustomer and Order tables with pointers


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For each customer who placed an order, what is theFor each customer who placed an order, what is thecustomers name and order number?customers name and order number?

SELECT CUSTOMER_T.CUSTOMER_ID, CUSTOMER_NAME, ORDER_IDSELECT CUSTOMER_T.CUSTOMER_ID, CUSTOMER_NAME, ORDER_ID

FROM CUSTOMER_T NATURAL JOIN ORDER_T ONFROM CUSTOMER_T NATURAL JOIN ORDER_T ON

CUSTOMER_T.CUSTOMER_ID = ORDER_T.CUSTOMER_ID;CUSTOMER_T.CUSTOMER_ID = ORDER_T.CUSTOMER_ID;

Join involves multiple tables in FROM clause

Natural Join ExampleNatural Join Example

ON clause performs the equality

check for common columns of the

two tables

Note: from Fig. 1, you seethat only 10 Customershave links with orders

Only 10 rows will bereturned from this INNER

join


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List the customer name, ID number, and orderList the customer name, ID number, and ordernumber for all customers. Include customernumber for all customers. Include customerinformation even for customers that do have an orderinformation even for customers that do have an order

SELECT CUSTOMER_T.CUSTOMER_ID, CUSTOMER_NAME, ORDER_IDSELECT CUSTOMER_T.CUSTOMER_ID, CUSTOMER_NAME, ORDER_ID

FROM CUSTOMER_T, LEFT OUTER JOIN ORDER_TFROM CUSTOMER_T, LEFT OUTER JOIN ORDER_T

ON CUSTOMER_T.CUSTOMER_ID = ORDER_T.CUSTOMER_ID;ON CUSTOMER_T.CUSTOMER_ID = ORDER_T.CUSTOMER_ID;

Outer Join ExampleOuter Join Example

(Microsoft Syntax)(Microsoft Syntax)

LEFT OUTER JOIN syntax withON causes customer data toappear even if there is nocorresponding order data

Unlike INNER join, this willinclude customer rows withno matching order rows

Why Customer data? Why not Order data?


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Results

UnlikeINNER

join, thiswill includecustomerrows withno

matchingorder rows


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Assemble all information necessary to create anAssemble all information necessary to create aninvoice for order number 1006invoice for order number 1006

SELECT CUSTOMER_T.CUSTOMER_ID, CUSTOMER_NAME,SELECT CUSTOMER_T.CUSTOMER_ID, CUSTOMER_NAME,CUSTOMER_ADDRESS, CITY, SATE, POSTAL_CODE,CUSTOMER_ADDRESS, CITY, SATE, POSTAL_CODE,

ORDER_T.ORDER_ID, ORDER_DATE, QUANTITY,ORDER_T.ORDER_ID, ORDER_DATE, QUANTITY,PRODUCT_DESCRIPTION, STANDARD_PRICE,PRODUCT_DESCRIPTION, STANDARD_PRICE,(QUANTITY * UNIT_PRICE)(QUANTITY * UNIT_PRICE)

FROM CUSTOMER_T, ORDER_T, ORDER_LINE_T, PRODUCT_TFROM CUSTOMER_T, ORDER_T, ORDER_LINE_T, PRODUCT_T

WHERE CUSTOMER_T.CUSTOMER_ID = ORDER_LINE.CUSTOMER_IDWHERE CUSTOMER_T.CUSTOMER_ID = ORDER_LINE.CUSTOMER_ID

AND ORDER_T.ORDER_ID = ORDER_LINE_T.ORDER_IDAND ORDER_T.ORDER_ID = ORDER_LINE_T.ORDER_IDAND ORDER_LINE_T.PRODUCT_ID = PRODUCT_PRODUCT_IDAND ORDER_LINE_T.PRODUCT_ID = PRODUCT_PRODUCT_ID

AND ORDER_T.ORDER_ID = 1006;AND ORDER_T.ORDER_ID = 1006;

Four tables involved in this join

Multiple Table Join ExampleMultiple Table Join Example

Each pair of tables requires an equality-check condition in the WHERE clause,

matching primary keys against foreign keys


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Figure 8-4 Results from a four-tablejoin

From CUSTOMER_T table

From ORDER_T table From PRODUCT_T table


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Processing Multiple TablesProcessing Multiple Tables

Using SubqueriesUsing Subqueries SubquerySubqueryplacing an inner query (SELECTplacing an inner query (SELECT

statement) inside an outer querystatement) inside an outer query

Options:Options:

In a condition of the WHERE clauseIn a condition of the WHERE clause As a table of the FROM clauseAs a table of the FROM clause

Within the HAVING clauseWithin the HAVING clause

Subqueries can be:Subqueries can be:

NoncorrelatedNoncorrelatedexecuted once for the entireexecuted once for the entireouter queryouter query

CorrelatedCorrelatedexecuted once for each row returnedexecuted once for each row returnedby the outer queryby the outer query


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Show all customers who have placed an orderShow all customers who have placed an order

SELECT CUSTOMER_NAME FROM CUSTOMER_TSELECT CUSTOMER_NAME FROM CUSTOMER_TWHERE CUSTOMER_ID INWHERE CUSTOMER_ID IN

(SELECT DISTINCT CUSTOMER_ID FROM ORDER_T);(SELECT DISTINCT CUSTOMER_ID FROM ORDER_T);

Subquery ExampleSubquery Example

Subquery is embedded inparentheses. In this case it

returns a list that will be used

in the WHERE clause of the

outer query

The IN operator will test to see if

the CUSTOMER_ID value of a

row is included in the list returned

from the subquery


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Correlated vs. NoncorrelatedCorrelated vs. Noncorrelated

SubqueriesSubqueries Noncorrelated subqueries:Noncorrelated subqueries:

Do not depend on data from the outerDo not depend on data from the outerqueryquery

Execute once for the entire outer queryExecute once for the entire outer query

Correlated subqueries:Correlated subqueries: Make use of data from the outer queryMake use of data from the outer query

Execute once for each row of the outerExecute once for each row of the outerqueryquery

Can use the EXISTS operatorCan use the EXISTS operator


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Figure 8-6a

Processing a

noncorrelatedsubquery

No reference to data inouter query, sosubquery executes once

only

These are the onlycustomers that haveIDs in the ORDER_Ttable

1. The subquery

executes andreturns thecustomer IDs fromthe ORDER_T table

2. The outer query on

the results of thesubquery


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Show all orders that include furniture finished inShow all orders that include furniture finished innatural ashnatural ash

SELECT DISTINCT ORDER_ID FROM ORDER_LINE_TSELECT DISTINCT ORDER_ID FROM ORDER_LINE_T

WHERE EXISTSWHERE EXISTS(SELECT * FROM PRODUCT_T(SELECT * FROM PRODUCT_T

WHERE PRODUCT_ID = ORDER_LINE_T.PRODUCT_IDWHERE PRODUCT_ID = ORDER_LINE_T.PRODUCT_ID

AND PRODUCT_FINISH = Natural ash);AND PRODUCT_FINISH = Natural ash);

Correlated Subquery ExampleCorrelated Subquery Example

The subquery is testing for a value that comes from the

outer query further explain: Order-Product-Order

The EXISTS operator will return a

TRUE value if the subquery resulted

in a non-empty set, otherwise itreturns a FALSE


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Figure 8-6b

Processing a

correlatedsubquery

Subquery refers to outer-

query data, so executes once

for each row of outer query

Note: only theorders thatinvolveproducts withNatural Ash willbe included inthe final results


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Show all products whose standard price is higher thanShow all products whose standard price is higher than

the average pricethe average price

SELECT PRODUCT_DESCRIPTION, STANDARD_PRICE, AVGPRICESELECT PRODUCT_DESCRIPTION, STANDARD_PRICE, AVGPRICE

FROMFROM(SELECT AVG(STANDARD_PRICE) AVGPRICE FROM PRODUCT_T),(SELECT AVG(STANDARD_PRICE) AVGPRICE FROM PRODUCT_T),

PRODUCT_TPRODUCT_TWHERE STANDARD_PRICE > AVG_PRICE;WHERE STANDARD_PRICE > AVG_PRICE;

Another Subquery ExampleAnother Subquery Example

The WHERE clause normally cannot include aggregate functions, but becausethe aggregate is performed in the subquery its result can be used in the outerquerys WHERE clause

One column of the subquery is anaggregate function that has an aliasname. That alias can then be referredto in the outer query

Subquery forms the derivedtable used in the FROM clauseof the outer query


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Union QueriesUnion Queries Combine the output (union of multiple queries)Combine the output (union of multiple queries)

together into a single result tabletogether into a single result table

First query

Second query

Combine


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Figure 8-7 Combining queries using UNION


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Conditional Expressions UsingConditional Expressions Using

Case SyntaxCase SyntaxThis is available withThis is available with

newer versions ofnewer versions ofSQL, previously notSQL, previously not

part of the standardpart of the standard

Figure 8Figure 8--88


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Tips for Developing QueriesTips for Developing Queries

Be familiar with the data model (entities andBe familiar with the data model (entities andrelationships)relationships)

Understand the desired resultsUnderstand the desired results

Know the attributes desired in resultKnow the attributes desired in result

Identify the entities that contain desiredIdentify the entities that contain desiredattributesattributes

Review ERDReview ERD

Construct a WHERE for each linkConstruct a WHERE for each link

Fine tune with GROUP BY and HAVINGFine tune with GROUP BY and HAVINGclauses if neededclauses if needed

Consider the effect on unusual dataConsider the effect on unusual data


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Ensuring Transaction IntegrityEnsuring Transaction Integrity

Transaction = A discrete unit of work thatTransaction = A discrete unit of work thatmust be completely processed or notmust be completely processed or notprocessed at allprocessed at all May involve multiple updatesMay involve multiple updates

If any update fails, then all other updates must beIf any update fails, then all other updates must becancelledcancelled

SQL commands for transactionsSQL commands for transactions BEGIN TRANSACTION/END TRANSACTIONBEGIN TRANSACTION/END TRANSACTION

Marks boundaries of a transactionMarks boundaries of a transaction

COMMITCOMMIT Makes all updates permanentMakes all updates permanent

ROLLBACKROLLBACK Cancels updates since the last COMMITCancels updates since the last COMMIT


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Figure 8-9An SQL Transaction sequence (in pseudocode)


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Data Dictionary FacilitiesData Dictionary Facilities

System tables that store metadataSystem tables that store metadata

Users usually can view some of these tablesUsers usually can view some of these tables

Users are restricted from updating themUsers are restricted from updating them

Some examples in Oracle 10gSome examples in Oracle 10g

DBA_TABLESDBA_TABLESdescriptions of tablesdescriptions of tables DBA_CONSTRAINTSDBA_CONSTRAINTSdescription of constraintsdescription of constraints

DBA_USERSDBA_USERSinformation about the users of the systeminformation about the users of the system

Examples in Microsoft SQL Server 2000Examples in Microsoft SQL Server 2000

SYSCOLUMNSSYSCOLUMNStable and column definitionstable and column definitions SYSDEPENDSSYSDEPENDSobject dependencies based on foreign keysobject dependencies based on foreign keys

SYSPERMISSIONSSYSPERMISSIONSaccess permissions granted to usersaccess permissions granted to users


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SQL:1999 and SQL:200SQL:1999 and SQL:200NN

Enhancements/ExtensionsEnhancements/Extensions

UserUser--defined data types (UDT)defined data types (UDT) Subclasses of standard types or an object typeSubclasses of standard types or an object type

Analytical functions (for OLAP)Analytical functions (for OLAP)

CEILING, FLOOR, SQRT, RANK, DENSE_RANKCEILING, FLOOR, SQRT, RANK, DENSE_RANK WINDOWWINDOWimproved numerical analysis capabilitiesimproved numerical analysis capabilities

New Data TypesNew Data Types BIGINT, MULTISET (collection), XMLBIGINT, MULTISET (collection), XML

CREATE TABLE LIKECREATE TABLE LIKEcreate a new tablecreate a new tablesimilar to an existing onesimilar to an existing one

MERGEMERGE


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Persistent Stored Modules (SQL/PSM)Persistent Stored Modules (SQL/PSM)

Capability to create and drop code modulesCapability to create and drop code modules

New statements:New statements: CASE, IF, LOOP, FOR, WHILE, etc.CASE, IF, LOOP, FOR, WHILE, etc.

Makes SQL into a procedural languageMakes SQL into a procedural language

Oracle has propriety version calledOracle has propriety version calledPL/SQL, and Microsoft SQL Server hasPL/SQL, and Microsoft SQL Server hasTransact/SQLTransact/SQL

SQL:1999 and SQL:200SQL:1999 and SQL:200NN

Enhancements/Extensions (cont.)Enhancements/Extensions (cont.)


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Routines and TriggersRoutines and Triggers

RoutinesRoutines Program modules that execute on demandProgram modules that execute on demand

FunctionsFunctionsroutines that return values androutines that return values and

take input parameterstake input parameters ProceduresProceduresroutines that do not returnroutines that do not return

values and can take input or outputvalues and can take input or outputparametersparameters

TriggersTriggers Routines that execute in response to aRoutines that execute in response to a

database event (INSERT, UPDATE, ordatabase event (INSERT, UPDATE, orDELETE)DELETE)


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Figure 8-10 Triggers contrasted with stored procedures

Procedures are called explicitly

Triggers are event-drivenSource: adapted from Mullins, 1995.


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Figure 8-11 Simplified trigger syntax, SQL:200n

Figure 8-12 Create routine syntax, SQL:200n


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Embedded and Dynamic SQLEmbedded and Dynamic SQL

Embedded SQLEmbedded SQL

Including hardIncluding hard--coded SQL statements in acoded SQL statements in aprogram written in another language such asprogram written in another language such asC or JavaC or Java

Dynamic SQLDynamic SQL

Ability for an application program to generateAbility for an application program to generate

SQL code on the fly, as the application isSQL code on the fly, as the application isrunningrunning


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OLAP SQLOLAP SQL

Online Transaction Processing (OLTP)Online Transaction Processing (OLTP) RealReal--time processing of SQL transactions,time processing of SQL transactions,

characterized by fast data entry and retrieval in multicharacterized by fast data entry and retrieval in multi--user environmentsuser environments

Smaller size, less data sources, many users, simplerSmaller size, less data sources, many users, simplerqueries, more normalized, standard SQLqueries, more normalized, standard SQL

Online Analytical Processing (OLAP)Online Analytical Processing (OLAP)

Use of graphical tools providing users withUse of graphical tools providing users with

multidimensional views of data for analysis purposesmultidimensional views of data for analysis purposes

Larger size, more data sources, fewer users, complexLarger size, more data sources, fewer users, complexqueries, less normalized, OLAP SQL and statisticalqueries, less normalized, OLAP SQL and statisticalpackages (SPSS/SAS)packages (SPSS/SAS)


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C8 - Advanced SQL